As computer technology has evolved, so too has the use of networks which communicatively couple computer systems together enabling remote computer systems to exchange information. One example of just such a network topology is the Ethernet standard topology, defined within the 802.3 standards committee of the Institute of Electronic and Electrical Engineers (IEEE). Over the last decade, the Ethernet standard has evolved from a 10 Mb/S standard to a 100 Mb/S standard to a 1 Gb/s standard and, more recently, a 10 Gb Ethernet standard, IEEE 802.3ae entitled Local and Metropolitan Area Networks—Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications—Media Access Control Parameters, Physical Layers and Management Parameters for 10 Gb/s Operation has been proposed, each of which are incorporated herein by reference.
As currently proposed, the 802.3ae Ethernet standard provides for a single, 10 Gb/s communication channel which is the aggregate of four lanes, each providing full-duplex data rate of 2.5 Gb/s of 8 b/10 b encoded data at a signaling rate of 3.125 Gb/s (or, 12.5 Gb/s for the aggregate channel). To place a 10 Gb/s data rate in context, the entire contents of a DVD could be transmitted through a 10 Gb/s link in less than six seconds. An example of an 802.3ae compliant network interface (NI) architecture is presented, with reference to FIG. 1.
Turning briefly to FIG. 1, a block diagram of a conventional 10 Gb/s network interface is presented. As shown, the conventional 802.3ae network interface includes a system bus interface 102, one or more input/output buffer(s) 104, an 802.3ae media access controller 106, an encoder/decoder 108 coupled to a 10 Gb/s attachment unit interface (XAUI) 110, and a 10 Gb/s transceiver 112. As used herein, the system bus interface 102 and the I/O buffers 104 effectively couple the 802.3ae MAC to processing elements of a host system. Content is received from the processing elements of the host via the interface 102 and buffered, as required, to/from the 802.3ae MAC. The 802.3ae MAC processes received data to facilitate communication over the network communication link. In this regard, 802.3ae MAC packetizes data for transmission, and de-packetizes information received from the communication link for promotion to the host processing elements. The 802.3ae MAC is coupled to an Encoder/Decoder 108 to provide signaling for packing 2×1 G channels into a single 2.5 G XAUI channel.
The 10 G external attachment unit interface (XAUI) is depicted comprising four (4) channels, which establish four full-duplex communication “lanes”, which are aggregated to provide the 10 Gb/s communication link through a physical media interface 112 (e.g., an optical transceiver). The XAUI interface 112 is used to extend the effective transmission length of the 802.3ae MAC, facilitating more flexibility in connecting the 802.3ae MAC to the physical media interface. In this regard, the XAUI interface performs additional encoding using the 8 b/10 b encoding scheme such that each of the four channels supports a data rate of 2.5 Gb/s over a signaling rate of 3.125 Gb/s (the difference allocated to encoding overhead). It will be appreciated that the physical media interface 112 may also perform additional coding (e.g., 64 b/66 b) in preparing the content for transmission over the physical medium.
While the impressive throughput of the 10 Gb Ethernet architecture offers the promise of eliminating network processing bottlenecks for a significant time to come, those skilled in the art will appreciate that current computing platforms cannot consume data at this rate. Thus, current implementations of a 10 G Ethernet architecture will necessarily require significant buffering between 802.3ae compliant devices and more traditional computing resources (e.g., client computers, host systems, servers, and the like) to enable the conventional computing device(s) to consume data in accordance with its processing capabilities.
Another significant limitation lies in the fact that, as proposed, 802.3ae devices will not interoperate with legacy Ethernet interface(s) at the link-level (i.e., in the parlance of the Open Systems Interconnect (OSI) communication model). That is to say, unlike legacy Ethernet standards which provide for link-level compatibility by having the device “fall back” to the lowest common communication denominator (e.g., 10 Mb, 100 Mb or 1 Gb data rates), the proposed 802.3ae standard does not provide for such link-level compatibility with conventional Ethernet devices. This lack of backwards compatibility fails to offer consumers a migration path that allows them to upgrade individual components of a network as the need arises. Given the popularity of past Ethernet architectures, consumers have a significant investment in their Ethernet networking architecture and, consequently, are not likely to simply replace such network elements wholesale to make this upgrade.
Thus, while the 802.3ae standard proposal provides a roadmap of the future of Ethernet, a number of limitations stand in the way of early acceptance and adoption in the marketplace of 802.3ae-compliant devices. First, the communication rate of 802.3ae devices can quickly overwhelm host systems without significant buffering at the interface. Those skilled in the art will appreciate that the memory elements and associated control to provide such buffering add significant cost to the conventional 802.3ae interface.